Impervious cover, including all human-made structures such as homes, driveways, and parking lots, is associated with loss of watershed function and increased pollutant and sediment loading. Disturbance of sensitive areas like wetlands led the USDA Forest Service and TRPA to develop the Bailey land capability system in the early 1970s. The system assigned all land in the region to land capability classes ranging from 1 to 7, with capability 1 being the most environmentally fragile and sensitive to development. The Bailey system prohibits new development on all capability 1 through 3 parcels and restricts the amount of land coverage (i.e., pavement and building footprint) that can be placed on capability 4 through 7 parcels. Since the system’s adoption coverage has been removed from more sensitive areas, and new development focused on less sensitive areas. Parcel level verification of land capability class before development ensures that excess coverage is not added within a land capability class and removal of coverage from sensitive lands is facilitated by Environmental Improvement Program partners and the California and Nevada land banks through the Excess Coverage Mitigation Program. 

Since adoption, there have been questions about the feasibility and cost-effectiveness of attainment of the coverage target for the most sensitive lands (1b). Attainment would require the unlikely removal and/or relocation of 8.3 percent of all impervious cover in the Region, including removal and buyout (with transfers or retirement) of large portions of existing private development (residential, tourist, commercial) in the Region’s communities.



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Note: Thresholds reported as "Implemented" refer to thresholds that were adopted as policy guidance in the development of the Regional Plan. In these cases, the subject policies, ordinances, or environmental protections have been incorporated into the TRPA Regional Plan and TRPA Code of Ordinances.